Today I tried to update some of my custom cache lists in Milestones tab and add a new one. All but one of the original lists vanished on the first attempt and eventually just the new custom cache list remained.

I mean Custom cache lists in Profile stats. And yes, I clicked "Save" button as the help always reminded me to :(
It could be just some random database hickup but as I did not find it in the hellp system I report it ...